The short answer is no, we can't. There are mental issues which can cause someone to act - and even kill - in ways they normally wouldn't. It's extreme, obviously, but it happens. That said, and speaking generally, if someone knows they have these issues, it is their responsibility to control the situation as best they can, whether through therapy, drugs, removal from stressors, or whatever else they need to do.

Now, specifically, I can't say, of course, because I - like most of the rest of us - know a whole lot of nothing about Belcher or why he did this.

That's all I want to say, and I don't want this to become All About Mental Health, so I won't go down this rabbit hole any farther, at least not in this thread.